1. Field of the Invention
This invention relates to the field of information networks, and more particularly relates to a method and system for conveying information over a network.
2. Description of the Related Art
Today's networks carry vast amounts of information. High-bandwidth applications supported by these networks include streaming video, streaming audio, and large aggregations of voice traffic, among other such applications. In the future, these demands are certain to increase. To meet such demands, an increasingly popular alternative is the use of lightwave communications carried over fiber-optic cables. The use of lightwave communications provides several benefits, including high bandwidth, ease of installation, and capacity for future growth.
In this new age of data-centric communication networks, the ability to support terabit rate routing in the network core is becoming a more common requirement. In an effort to make terabit routing a reality, such technology needs to be economical, as well as being efficient in design and integration. Ease of use and serviceability are also important. An efficient design involves framing protocols, integrated hardware and software, and network design as a whole. If addressed, such a solution results in a highly economical and deployable communications system.
Over the next five years, the growth projected by major service providers (e.g., UUNet, AT&T and Sprint) in their data (IP) networks is exponential. The architecture of such high-bandwidth backbone networks have, among others, at least three important properties:                1. Such networks tend to be made up of a relatively small number of switching/routing nodes interconnected by very high bandwidth links. The aggregate capacity of each of such links is projected to go beyond 40 Gbps in the near future, with even higher speeds to follow.        2. As the amount of traffic increases, the bandwidth required between these nodes will increase, but the number of nodes is expected to remain relatively constant.        3. These switching nodes tend to be widely dispersed, geographically, with large inter-node distances (e.g., typically over 1000 km).        
The synchronous optical network (SONET) protocol is among those protocols employed in today's optical infrastructures. SONET is a physical transmission protocol capable of transmission speeds in the multi-gigabit range, and is defined by a set of electrical as well as optical standards. SONET's ability to use currently-installed fiber-optic cabling, coupled with the fact that SONET significantly reduces complexity and equipment functionality requirements, has given local and interexchange carriers incentive to employ SONET. Also attractive is the immediate savings in operational cost that this reduction in complexity provides. SONET thus allows the realization of high-bandwidth services in a more economical manner than previously existed.
Today, the bandwidth requirements of communications between the core packet switches using SONET have increased from 2.5 Gbps (OC-48 in the SONET standard) to 10 Gbps (OC-192 in the SONET standard) in some cases. Routers with single OC-48- or OC-192-capable port cards and a transport system that can carry such a data rate over a single wavelength have supported these increases.
While the port speeds of routers can (and likely will) be increased beyond 10 Gbps, the transport systems presently in place are unable to transport such high-speed datastreams (e.g., a 40 Gbps (or greater) datastream) using currently-installed fiber-optic cabling, at least without expensive (and frequent) regeneration. This inability to economically transport such higher-speed datastreams (i.e., beyond 10 Gbps) over long distances using currently-installed fiber-optic cabling is an obstacle to deployment of high-speed transport at the network core.
Moreover, the efficiency (the amount of data versus the overall size of a frame) provided by SONET is somewhat less than desirable. A SONET frame provides an efficiency of about 96.2%. This means that 3.8% of the available bandwidth is consumed by overhead (or is unused). In the case of an OC-192 signal, for example, this equates to wasted bandwidth of about 378 Mbps. Given the costs associated with providing bandwidth at such data rates, this overhead represents appreciable lost revenues. While 100% efficiency is unlikely, given that some overhead is typically required, it is still desirable to improve the efficiency provided by available communication channels.
One possible alternative to increasing the bandwidth of the connections between core routers is to grow the existing port count and use multiple ports between routers. Although this seems logical from the perspective of the connection, this alternative is not very scalable or economical because the IP forwarding table per port increases linearly and the total memory required for the forwarding table increases as N2 (where N=number of ports). The large port count also involves larger space and power requirements that add to the cost of this solution.
The definition of a framing protocol and mechanism that support a solution to this predicament are thus required. Such a protocol and mechanism should be efficient and easily implemented in various hardware architectures. Moreover, such a protocol and mechanism should exhibit high functional accuracy that is verifiable via simulations.